矽基板在鹼性溶液中之蝕刻表面形貌與反應機制研究

Study on the surface morphology and reaction mechanism of silicon by alkaline etching method

在先進半導體製程與微機電系統元件製備的重要關鍵技術中，濕式化學蝕刻扮演著相當重要的角色。為了徹底掌握技術與原理，進而有效發揮其製程優點與特性，本研究以改變蝕刻製程條件，如矽基板晶體方向、蝕刻液濃度與溫度，探討非等向性蝕刻的反應機制，並觀察基材受到化學蝕刻作用所形成的特殊表面形貌。在非等向性蝕刻實驗中，在矽(100)基板上會形成金字塔的表面形貌；在矽(110)基板則會形成V形槽，而在矽(111)基板上會形成階梯或是三角形的凹坑。改變蝕刻液的濃度，矽(111)基板與矽(100)基板的特徵表面形貌會隨著濃度提高而減少，而矽(110)基板的特徵表面形貌會隨著濃度提高而變得明顯。改變蝕刻液的溫度，隨著提高溫度會使蝕刻速率變快，分子之間的碰撞頻率變高，在三個晶體平面上生成的表面形貌均呈現減少的趨勢。在添加異丙醇的實驗中，發現異丙醇使基板(110)凸起的表面受抑制，而在基板(100)平面則會生成均勻分布的小丘。

 

Wet chemical etching has become an important technique in the manufacture of semiconductor and MEMS systems. To better understand and well control this technology, in this study the reaction mechanisms of anisotropic chemical etching with characteristic surface morphologies are investigated under various etching conditions, including the differences in the crystal orientation, the concentration of potassium hydroxide and the temperature. From the results of the anisotropic etching experiments, a pyramid-like surface morphology of Si(100) etched with potassium hydroxide are formed, while a V-groove of Si(110) and steps or triangular pits of Si(111) are observed. The characteristic surface morphologies of Si(111) and Si(100) would be reduced with the increase of the potassium hydroxide concentration, and an enhanced surface morphology in Si(110) is obtained. Owing to the high frequency of collisions between molecules, the surface morphologies of Si would be flattened as the temperature is increased. Meanwhile, the etch rate of potassium hydroxide becomes faster with increasing the temperature. It is also found that the isopropanol can alter the featured surface morphologies of Si(100) and Si(110)